Experiments
- Electroscope
- In order to visualize the Charge , we have a Glass Jar in which two aluminum foils are suspended from a ring and connected to an aluminum road and a disc is attached out side.
- As we rub a plastic ball on any cloth and bring it close to disc the foils are repelled from each other due to Induction of identical CHARGE on them caused by induction.
- Due to friction in plastic ball, a few electrons are removed away so that it becomes partially negatively charged. As we bring it close to Metallic disc, Free electrons are repelled leaving partially negative charge on suspended foils starts repelling.
- As we touch the metallic disc the induced charge goes to ground.
- Electromagnetic Induction
- We have a Spring- Mass system to oscillate at about 1 Hz. It oscillates in a vertical line around a mean position. We have attached a strong magnet with its poles along the vertical line. A copper coin about 3000 turns is placed at mean position.
- As the Oscillator moves up and down, the magnetic field associated with the coil changes and electric current is generated in the coil as we connected a light emitting diode LED across the coil starts glowing.
- It glows only half the oscillation cycle and its brightness Reduces as it slows down.
- This follows the Faraday’s laws of E M Induction.
- Mel die’s Experiment
- In This experiment , a speaker vibrates due to AC source 6 volts from a transformer. These vibrations travels in string generate the wave pattern in limited length and tension in the string.
- At a particular setting we can observe at several Locations the string is vibrating with large amplitude And other locations as no vibrations, we call them Anti nodes and Nodes.
- This wave pattern with stable situation of nodes and antinodes is called Stationary Wave.
- The stationary wave pattern depends upon the Length, tension and string (mass per unit length)
Eddy Currents Experiment
- In this experiment, AC current flow through the Bulb And a copper coil about 2000 turns, (28-30 swg) With a bell switch. About 150 iron wires of 12” ( bicycle spokes) are kept in 40 mm PVC tube.
- Aluminum rings (bangles) are free to move over the PVC tube.
- As the switch is ON, the rings jump.
- Due to AC current, alternating magnetic field is Generating across the PVC tube, that generates current
- In the aluminum rings. Called Eddy currents.
- This also generate magnetic Field to oppose the ac field due to Lenze’s effect, responsible for the levitation of aluminum rings.